distance from point to line segment…

gistfile1.numpy

from numpy import arccos, array, dot, pi
from numpy.linalg import det, norm

def distance(A, B, P):
    """ segment line AB, point P, where each one is an array([x, y]) """
    if all(A == P) or all(B == P):
        return 0
    if arccos(dot((P - A) / norm(P - A), (B - A) / norm(B - A))) > pi / 2:
        return norm(P - A)
    if arccos(dot((P - B) / norm(P - B), (A - B) / norm(A - B))) > pi / 2:
        return norm(P - B)
    return abs(dot(A - B, P[::-1]) + det([A, B])) / norm(A - B)

The last return on line 12 was wrong. This works instead:

from numpy import arccos, array, dot, pi, cross
from numpy.linalg import det, norm

# from: https://gist.github.com/nim65s/5e9902cd67f094ce65b0
def distance_numpy(A, B, P):
    """ segment line AB, point P, where each one is an array([x, y]) """
    if all(A == P) or all(B == P):
        return 0
    if arccos(dot((P - A) / norm(P - A), (B - A) / norm(B - A))) > pi / 2:
        return norm(P - A)
    if arccos(dot((P - B) / norm(P - B), (A - B) / norm(A - B))) > pi / 2:
        return norm(P - B)
    return norm(cross(A-B, A-P))/norm(B-A)

The last return on line 12 was wrong. This works instead:

from numpy import arccos, array, dot, pi, cross
from numpy.linalg import det, norm

# from: https://gist.github.com/nim65s/5e9902cd67f094ce65b0
def distance_numpy(A, B, P):
    """ segment line AB, point P, where each one is an array([x, y]) """
    if all(A == P) or all(B == P):
        return 0
    if arccos(dot((P - A) / norm(P - A), (B - A) / norm(B - A))) > pi / 2:
        return norm(P - A)
    if arccos(dot((P - B) / norm(P - B), (A - B) / norm(A - B))) > pi / 2:
        return norm(P - B)
    return norm(cross(A-B, A-P))/norm(B-A)

You did not handle the case where A equals B, which throws a true_divide. Something like this should be added:
if all(A == B): return dist(A, P)

I would also add a np.clip within arccos such that: arccos(np.clip(angle, -1, 1))